Multi-mode, Multi-band PA Module for LTE

The SKY77441 Power Amplifier Module (PAM) is one of the first products available specifically targeting Long Term Evolution frequency division duplex (TDD) bands 38 and 40. LTE TDD is expected to become a widely used 4G standard that mobile operators utilize in China and other parts of the world. According to Strategy Analytics, the global LTE handset market is expected to reach 150 million units by 2013.

The SKY77441 is a fully matched, surface-mount module developed for Long Term Evolution (LTE) and Evolved Universal Terrestrial Radio Access Network (EUTRAN) frequency division duplex (FDD) and TDD applications. Its compact size makes it ideal for mobile applications such as data cards and handsets. This small and efficient module packs full coverage of LTE FDD Band VII and LTE FDD Bands 38 and 40 into a single compact package, and is capable of delivering the linear wideband code division multiple access (W-CDMA) power up to 28.5 dBm from 2.3 to 2.7 GHz. The SKY77441 meets the stringent spectral linearity requirements of LTE modulation with quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) from 1.4 to 20 MHz bandwidth and up to 100 full or partial resource block allocations with high power-added efficiency.

Figure 1 Block diagram of SKY77441.

Integration of the PAM simplifies the design of the 4G-compatible handset radios and data cards as all the active RF circuitry, including the PA, input, interstage and output matching circuits and power detector are optimized within the single module component. See Figure 1 for a block diagram of the module. Output match is realized off-chip within the module package to optimize efficiency and power performance into a 50 Ω load. The device is manufactured with Skyworks’ InGaP BiFET process that provides for all positive voltage DC supply operation while maintaining high efficiency and good linearity. Primary bias to the SKY77441 is supplied via the VCC1 and VCC2 pads directly from a three-cell Ni-Cad, a single-cell Li-Ion, or other suitable batteries with outputs in the 3.0 to 4.6 V range, while the bias network is powered up with the VCCB pad. DC-DC converter operation can be supported with lower power operation down to 1.5 V. Power down is accomplished by setting a logic low level on the VEN pad. No external supply side switch is needed as typical “off” leakage is 100 microamperes with full primary voltage supplied from the battery. The VMODE pad is used to switch between high and low power modes to reduce current consumption and gain in the back-off conditions. VBA is used to further control the current consumption in the low power mode.

The SKY77441 delivers over 26 dBm of linear power output with full LTE resource block allocation under either QPSK, or 16QAM, and 28.5 dBm of linear output power under W-CDMA modulation. See Figure 2a and 2b for plots of gain versus Pout at 25°C at various frequencies and voltages for LTE QPSK and W-CDMA, respectively. Figures 3a and 3b show ACPR1 for LTE QPSK and W-CDMA modulations versus Pout at various frequencies and voltages. Figure 4 shows EVM versus Pout at various frequencies and voltages for W-CMDA. EVM is less than 2 percent up to 27 dBm at 3.1 V and up to 28 dBm at 3.4 V. Figure 5 shows a plot of the detector response for LTE QPSK at various frequencies and voltages. The module supports low-operating voltage down to 3 V with high power added efficiency and high reliability.

The SKY77441 is packaged in a low profile 16 lead, 4 x 4 x 0.85 mm surface-mount leadless package. The part uses Skyworks’ Green Packaging Technology so it is lead (Pb) free, Restriction of Hazardous Substances (RoHS) compliant, conforms to the EIA/EICTA/JEITA Joint Industry Guide (JIG) Level A guidelines, and is free from antimony trioxide and brominated flame retardants.

The SKY77441 is a multi-mode, multi-band LTE PAM that enables enhanced talk, viewing and broadcast times while complying with the stringent linearity requirements across wide frequency ranges for use in data cards, handsets and other applications where compact size and high performance are needed.